Our Low Orbit Helium Assisted Navigator experimental flying truss is just about poised for lift-off, but before it leaves the ground we thought we'd update LOHAN fans on the proposed test rigs. Apprentice boffin Katarina poses with the finished truss Click here for a bigger version of the LOHAN graphic Our initial plan was …
Single balloon elevated
Could either make the truss T-shaped so the top end suspension clears the wings on launch, or invert it so the launch rail is underneath avoiding the lines altogether.
Re: Single balloon elevated
Yes - we could sling the aircraft under the truss, in which case the weight might help keep the thing more stable.
Re: Re: Single balloon elevated
Agreed. That was the 1st thing that came to mind for me. I see no need to change the truss. Just have the flat side on the bottom perhaps. I'm eager to see the launch rail (or whatever system you choose to use).
Re: Re: Single balloon elevated
How about a rhombus shaped truss, top end attached to balloon(s), bottom end has electronics etc for stability, with the launch vehicle attached to the 'underside' of one side of the lower part of the rhombus, so it is pointing upwards, angle depending on angle of rhombus.
Re: Single balloon elevated
A "T" shaped truss is spot on! Just use the 3 ends as suspension points, triangles are more stable anyway, then decide which way up to mount the truss.
To reduce spin, a tail something like that of a kite's would help. Due to the ascent their is bound to be air flowing downwards with some horizontal vector to it.
have the rocket at the very end of the truss and tie the tether lines for that end one or two joints back? This way the rocket is already clear of the tethers and even if LOHAN is spinning like mad, the rocket should still clear when it launches.
Re: why not
For some reason that made me think of the insane spinning rocket contraption designed by the nazis. Can't think of the name though
Never mind the theory, go empirical.
The tried and trusted method of boffins through the ages (just so long as trial and error doesn't include that nice Sir Terence Pratchett's alchemists)
Triple Orb Configuration...
Re: Triple Orb Configuration...
I saw that in 'Total Recall' years aqo!
Start the reactor!
Re: Re: Triple Orb Configuration...
Three tits? Awesome.
Why assume you have to launch from the top?
Another fan of the 'hang the launch vehicle below the truss' school of orbiting...
so how big ...
... do these ballons they get before they burst?
Re: so how big ...
well the real meteo balloons that I bought for around 5 euro each were 60cm diameter at ground level - swelling to around 3 metres diameter just before burst? allegedly, I'm just a random guy in a pub!
One or two orbs?
In fact you can avoid the risk of two of them taking the truss vertical by tying them together - above the level of the joing swivel. (just thinking of your preferred headline here!)
Two would also give more lifting capacity
in fact if the truss is long enough you could launch vertically from one end - sticking out past the baloon. You could counterweight it by putting the payload at the other end.
I hope you are going to test that the truss won't crumple into flames the microsecond that the rocket motors start.
It had crossed my mind...
Surely there's not enough oxygen at the launch altitude for the truss to be ignited?
Re: Re: Testing
There could still be enough heat and exhaust to crumple the truss in some manner that changes the launch orientation of LOHAN and sends her off into an unintended direction/obstacle.
Re: Re: Re: Testing
If the truss is carbon fibre it is unlikely to melt or crumple when subjected to a second or two of rocket exhaust. Most likely it'll just char a little bit.
Re: Re: Testing
The exploding-into-flames issue can be solved while increasing initial acceleration, by use of a piston launcher. I have launched rockets from a launcher made of 100% flammable materials (hardwood, balsa and cardboard with no protective coatings) and the piston-launcher does an amazing job of containing the gases while they burned. Caveat: I was using black-powder, not APCP. Be empirical.
The piston launcher will allow you to use the mass of your launch rail and electronics as an inertial anchor and also to get much more efficient use of the first burst of exhaust gases. It works like this: you attach a body tube to the end of the rocket motor using a friction fit. The body tube has external sanded-down centering rings that allow a slightly larger tube to slide freely around it while still maintaining a reasonably airtight seal. The larger tube is closed off at the back end and is solidly anchored to the launcher structure (it faces substantial net forces upon launch). The inner and outer tubes should be connected with a line to disconnect the inner tube from the engine after they pull apart from each other.
When the motor fires it compresses the interior of the tubes, exerting a powerful force on the plane (and, per Newton, on the launch rig) as the two tubes separate. It also contains most of the exhaust from the initial milliseconds of burn, protecting the rig quite effectively.
Sounds good; the one thing that needs to be taken into account is the contraction of both tubes at the temperature present at the intended launch altitude.
That should not be too much of a problem; the seals don't need to be really tight since they don't hold pressure for many milliseconds. Leakage is okay. Adjusting the pieces so they slide smoothly and easily coming out of a standard freezer is probably good enough.
You all probably know about these, but try searching for MD80 on ebay. Ignore the minidiscs and the remainder will be cheap self contained video cameras that record onto micro SD cards. Good for about an hour on a full charge, so maybe not long enough for the flight, but worth looking at. I've flown these on a kids kite with very little wind.
For a moment I thought you were suggesting they swing an airliner under the balloon...
Angled launch ramp
How about the single balloon elevated idea but with an angled launch ramp like an aircraft carrier , should clear the end truss cable and angle you below the balloon.
OccupyD CyberSpace/ for Every IntelAIgent Feed of Need to Seed to Serve to Sow New AI Feeds/Fields
Whatever next, El Reg? A Manned Ascent in Helium Balloon Pockets, which is the Core Reality of that Adventurous Future Derivative ZerodDay Trade.
Prior Martian missive achieved greater 3rd orbit accessibility. With regret, temporal necessities obstructed my inner script kid from constructing the requisite paired response to the chingychongy.
Man rags, or just the 1?
Why not toss the truss, hang Lohan by her nose on a long string and light her torch? Hang the camera halfway up the top string. Tie a counter weight to her ass with the same string for stability. The balloon should climb out of the way when the weight is released while Lohan picks up speed. this should drop off when the string burns and release the top balloon too. If anything bursts, it's going to be a disaster anyway, especially if there's all that crap hanging around everywhere.
The aircraft will be initially dynamically unstable. Without a launch rail of some sort it would just flutter around pointlessly instead of flying.
I like the new idea. I think some sort of droge (?sp?) hanging behind the assembly to stabilise the lauch is a good idea. it will rotate the assembly into the wind and stop the rotation. Think weather vane/cock
Need a stabliser for yaw
PARIS had a major issue with being swirled around as it rose. The obvious answer is indeed a vertical vane stabiliser or a small chute. Obviously a vane adds two parasitic weights: the vane itself at one end of the truss and a counterweight at the other. The drogue chute looks much more attractive. It could even be a windsock, like a sea anchor for a boat.
Re: Need a stabliser for yaw
Somebody is sure to say that this can't work. The point is that the centre of drag is different from the centre of mass, and that can be stable, but it needs an airflow, which you don't really get as you drift down-wind. A sea-anchor does work, but it is taking advantage of the two different working fluids, air and water, and their different behaviour.
It only needs slow relative movement of the sea anchor in the water to stabilise the boat. The wind-generated surface waves aren't always moving in the same direction as the local wind, and that is when things get complicated.
No, I don't think this will work. It's about as much sense as putting sails on a Zeppelin.
Re: Re: Need a stabliser for yaw
Centre of drag??
When I used to fly microlights, someone came up with the most stupid suggestion to blu-tak a piece of cotton to the front strut, thus one could tell from which direction the airflow was coming.
It made its way into the BMAA (British Microlight Aircraft Association)' monthly rag.
No-one thought that, if the plane is flying forward, in whatever air was about, it'd always point backwards. Dullards.
Re: Re: Re: Need a stabliser for yaw
Still, and yet, I assume that there is some sort of inertial delay between a shift in wind direction, and a equivalent shift in contraptional direction? If so, a vane would/should/could [?] still be useful in terms of stability.
I might go so far as to say that such a vane could ONLY work if there were inertia and constant shifting winds; but that the analogue imperative (I just made that up, wondrous what a few extra beers can do) guarantees that there will be such.
At least, I'd heartily (read: boozily) recommend that lightweight vanes are tested on the truss tests to verify my vanity.
I insist that the balloon[s] are topped off with great big throbbing erect nipples... err, to improve the vertical ascent aerodynamics.
You can also put huge chainsaws on the leading edge of the wings to cut the guy ropes on release.
Also useful for landing if any trees or people get in the way.
I'm not sure why, probably something to do with mechanics, but aren't balloon nipples normally used for inflation, and underside... As for the throbbing, I'm far to innocent to have ever witnessed nipples dangling down from above, let alone throbbing ones!
Here's my single-balloon idea!
Put the battery/avionics pack at one end of the truss, then LOHAN facing off the other end of the truss, with facing oriented 180 degrees from the battery pack . Have the cabling to the balloon go to two cables attached to the truss, one longer cable attached at the battery/avionics pack and the second , shorter cable attached a foot or two behind LOHAN, so the truss is held at an inclined angle of 45 degrees to maybe 70 degrees. That way the heavy battery pack provides stability on the truss and LOHAN will fire at an upward angle without having cables to avoid and clear the single balloon!
Now, having proved that this rocket science stuff is easy, I return to the harsh mistress that is marketing... :)
Re: Here's my single-balloon idea!
Dynamical instability is the problem. Now go back to your marketing "work".
Double balloon with tension lines
Take the double balloon setup, run tension lines from the bottom of each support line (at the end of the truss) to the top of the other support line (just under the balloon) . Launch at a slight angle to avoid hitting the crossing lines.
That should fix the problem of one balloon going higher than the other.
Re: Double balloon with tension lines
Did You mean...
A vertical line from each balloon to the end of the truss it's above, another diagonal line from each balloon to the opposite end of the truss?
with the higher balloon now providing more lift, the lower balloon has less work to do, so can rise and maintain equilibrium.
To prevent LORAN hitting the lines, mount it on a small pier at 90 degrees from the centre of the truss. Have a similar 'pier' on the other side with a counterweight, to maintain balance.
This could easily be tested with a couple of cheap party helium-filled balloons (naturally, not 'scientifically filled - there will be an imbalance) , some strong fishing nylon line, a long bit of bamboo (to replicate the truss) and an observer about a couple of kilometres away - preferably on a hill - , armed with a humongously good telescope, or a big telephoto lens on a tripod-mounted (video?) camera. Material cost? About a tenner.
Just a thought.
Truss, indeed! "I thank you for your support. I shall wash it and return it presently"
Yes, you did. I missed a word. Sorry.
If you go with two orbs, err, balloons, you just need to give them a massive, identical electrostatic charge so that they repel each other. A few million Volts should do.
Err, was that lightning? :-(
P.S. Hey, I may have discovered a fact of nature! So that's what keeps those things apart!
Could make for a shocking experiment.
The helium balloons are now to be referred to as 'Bulgarian Airbags'. Well, they'll save a playmobil 'naught from a fate worse than meltdown, I expect....
Fund Raising Banner Idea...
AN APPEAL ON BEHALF OF THE NATIONAL TRUSS
(Cannot tell a lie. Stole that from Monty Python)
The model I saw earlier had a V tail. This is ideal for using Delrin LOW DRAG Rail Buttons on the top of the rocket plane body and hang it on a Standard Launch Rail that runs along the bottom of the truss.
You can't perch a plane of any weight on top of a hanging truss. Long before it reached launch altitude it would simply flip over, fall off and auger into the ground. Keep the center of gravity low and hang the plane under the truss, out of the way of the suspension lines.
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